﻿using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using AMS.DataAccess.Sql;

namespace AMS.DataAccess.DatabaseSchema
{
    /// <summary>
    /// 用于获取SQL SERVER数据库信息的辅助类。它提供了一些SQL语句用于此目的
    /// </summary>
    public class SqlServerDB
    {
        /// <summary>
        /// 获取所有的用户表
        /// </summary>
        /// <returns></returns>
        public static string GetAllUserTables()
        {
            SqlBuilder sql = new SqlBuilder();
            sql.Add("SELECT name FROM sysobjects WHERE type = 'U'");
            sql.Add("ORDER BY name ASC");
            return sql.ToString();
        }

        /// <summary>
        /// 获取一个表的所有列
        /// </summary>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public static string GetColumns(string tableName)
        {
            SqlBuilder sql = new SqlBuilder();
            sql.Add("select c.name, c.length, c.prec, c.scale, c.usertype, c.status, c.isnullable, t.name as typename");
            sql.Add("from syscolumns c left join systypes t on c.xtype = t.xusertype");
            sql.Add(string.Format("where c.id = object_id({0})", AMS.DataAccess.SqlStringUtils.QuotedString(tableName)));
            sql.Add("order by c.colid ASC");
            return sql.ToString();

        }

        /// <summary>
        /// 获取一个表的所有列
        /// </summary>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public static string GetColumns2(string tableName)
        {
            SqlBuilder sql = new SqlBuilder();
            sql.Add(@"SELECT 
    TableName=CASE WHEN C.column_id=1 THEN O.name ELSE N'' END,
    TableDesc=ISNULL(CASE WHEN C.column_id=1 THEN PTB.[value] END,N''),
    Column_id=C.column_id,
    ColumnName=C.name,
    PrimaryKey=ISNULL(IDX.PrimaryKey,N''),
    C.is_identity,
    c.is_computed,
    Type=T.name,
    Length=C.max_length,
    Precision=C.precision,
    Scale=C.scale,
    C.is_nullable,
    [Default]=ISNULL(D.definition,N''),
    ColumnDesc=ISNULL(PFD.[value],N''),
    IndexName=ISNULL(IDX.IndexName,N''),
    IndexSort=ISNULL(IDX.Sort,N''),
    Create_Date=O.Create_Date,
    Modify_Date=O.Modify_date,
    IDX.key_ordinal
FROM sys.columns C
    INNER JOIN sys.objects O
        ON C.[object_id]=O.[object_id]
            AND O.type='U'
            AND O.is_ms_shipped=0
    INNER JOIN sys.types T
        ON C.user_type_id=T.user_type_id
    LEFT JOIN sys.default_constraints D
        ON C.[object_id]=D.parent_object_id
            AND C.column_id=D.parent_column_id
            AND C.default_object_id=D.[object_id]
    LEFT JOIN sys.extended_properties PFD
        ON PFD.class=1 
            AND C.[object_id]=PFD.major_id 
            AND C.column_id=PFD.minor_id
--             AND PFD.name='Caption'  -- 字段说明对应的描述名称(一个字段可以添加多个不同name的描述)
    LEFT JOIN sys.extended_properties PTB
        ON PTB.class=1 
            AND PTB.minor_id=0 
            AND C.[object_id]=PTB.major_id
--             AND PFD.name='Caption'  -- 表说明对应的描述名称(一个表可以添加多个不同name的描述)  

 LEFT JOIN                       -- 索引及主键信息
    (
        SELECT 
            IDXC.[object_id],
            IDXC.column_id,
            Sort=CASE INDEXKEY_PROPERTY(IDXC.[object_id],IDXC.index_id,IDXC.index_column_id,'IsDescending')
                WHEN 1 THEN 'DESC' WHEN 0 THEN 'ASC' ELSE '' END,
            PrimaryKey=CASE WHEN IDX.is_primary_key=1 THEN N'Y'ELSE N'' END,
            IndexName=IDX.Name,
            IDXC.key_ordinal
        FROM sys.indexes IDX
        INNER JOIN sys.index_columns IDXC
            ON IDX.[object_id]=IDXC.[object_id]
                AND IDX.index_id=IDXC.index_id
        LEFT JOIN sys.key_constraints KC
            ON IDX.[object_id]=KC.[parent_object_id]
                AND IDX.index_id=KC.unique_index_id
        INNER JOIN  -- 对于一个列包含多个索引的情况,只显示第1个索引信息
        (
            SELECT [object_id], Column_id, index_id=MIN(index_id)
            FROM sys.index_columns
            GROUP BY [object_id], Column_id
        ) IDXCUQ
            ON IDXC.[object_id]=IDXCUQ.[object_id]
                AND IDXC.Column_id=IDXCUQ.Column_id
                AND IDXC.index_id=IDXCUQ.index_id
    ) IDX
        ON C.[object_id]=IDX.[object_id]
            AND C.column_id=IDX.column_id 

-- WHERE O.name=N'要查询的表'       -- 如果只查询指定表,加上此条件
-- ORDER BY O.name,C.column_id
WHERE ");
            sql.Add(new SqlExpression("O.name", tableName));
            sql.Add("ORDER BY O.name,C.column_id");

            return sql.ToString();
        }
    }

}
